Endo record of dental sciences and technology in india in india in india in india in india in india india in india in india

1. FUNDAMENTAL CONCEPTS IN
CAVITY PREPARATION

2. Introduction
• Complete removal of the damaged tooth structure.
• The tooth as well as the restoration must be made strong enough to
withstand masticatory forces
• The tooth must be prepared in such a way that the restoration stays
within the prepared cavity.

3. TOOTH PREPARATION
SIMPLE:
If one tooth surface is
involved
COMPOUND:
If two tooth surface is
involved
COMPLEX:
If preparation involves
three or more surfaces

4. TOOTH PREPARATION WALLS
INTERNAL WALL:
Prepared surface that does not extend to the
external tooth surface
TWO TYPES:
1. AXIAL WALL:
Is an internal wall that is oriented parallel
to the long axis of the tooth.
2. PULPAL WALL:
Is an internal wall that is oriented
perpendicular to the long axis of the
tooth and is located occlusal to the pulp.
EXTERNAL WALL:
Is a prepared surface that extends
to the external tooth surface .

6. TOOTH PREPARATION ANGLES
The junction of two or more prepared surface is referred to as angle.
LINE ANGLE:
Is the junction of two planar
surfaces of different orientation
along a line
INTERNAL LINE ANGLE:
Is the line angle whose apex
points into the tooth
EXTERNAL LINE ANGLE:
Is the line angle whose apex
points away from the tooth
POINT ANGLE:
Is the junction of three planar
surfaces of different orientation.

7. CLASS I CLASS II

8. TOOTH PREPARATION LINE ANGLE POINT ANGLE
Class I 8 4
Class II 11 6
Class III 6 3
Class IV 11 6
Class V 8 4
CLASS III

9. CAVOSURFACE ANGLE:
Is the angle of tooth structure formed by the junction of a
prepared wall and the external surface of the tooth.

10. Tooth preparation
INTRA-CORONAL
Tooth preparation that leaves
much of the clinical crown surface
uninvolved
EXTRA-CORONAL
Tooth preparation that involves all
external enamel surfaces
Referred as “stumplike”

11. CLASSIFICATION OF TOOTH PREPARATION
ACCORDING TO GV BLACK:
CLASS I: Carries in the pit and fissures of occlusal
surfaces of molars and premolar
Carries in the occlusal two-thirds of the
facial and lingual surfaces molars
Carries in the lingual surfaces of maxillary
anteriors.
CLASS II: Carries in the proximal surfaces of molars and
premolars
CLASS III: Carries in the proximal surfaces of anterior
teeth without involving the incisal angle

12. CLASS IV:Carries in the proximal surfaces of
anterior teeth with involvement of the incisal
angle
CLASS V: Carries seen at the gingival third of the
facial and lingual surfaces of anterior and
posterior teeth
CLASS VI: Carries found in the incisal edge of
anterior teeth and cusp tips of posterior teeth
SIMON

13. BURS
• ROUND BUR – Punch cut
• STRAIGHT BUR- Cavity preparation
• INVERTED BUR – Producing convergence and undercuts
• TAPERED FISSURED BUR- Refine shape of the cavity, smooth and
parallel walls

14. Cavity preparation/Tooth preparation
• This is defined as the mechanical alteration of a defective, injured or
diseased tooth in order to best receive a restorative material which
will re-establish a healthy state for the tooth including esthetic
corrections , when indicated, along the normal form and function.

15. STAGES IN CAVITY PREPARATION
INITIAL CAVITY
PREPARATION
• STEP 1: Outline form
• STEP 2: Primary Resistance form
• STEP 3: Primary Retention form
• STEP 4: Convenience form
FINAL CAVITY
PREPARATION
• STEP 5: Removing any remaining enamel pit or fissure,
infected dentin, or defective old restorative material
• STEP 6: Pulp protection
• STEP 7: Secondary resistance and retention form
• STEP 8: Finishing the external walls and margins
• STEP 9: Final procedure- cleaning, inspecting, varnishing
and conditioning

16. STEP 1: OUTLINE FORM AND INITIAL DEPTH
• It is the placement of the preparation margin in the position they will
occupy in the final preparation , except for finishing the enamel walls
and margins . it also includes preparing an initial depth of 0.2-0.5mm
pulpally beyond DEJ

17. PRINCIPLES:
• Remove all friable or weakened enamel
• Include all faults
• Place margins of the cavity preparation such that good finishing of the margins
of the restoration is possible.
FEATURES:
1. Preserve cuspal strength
2. Preserve marginal ridge strength
3. Minimize faciolingual extensions
4. Use enameloplasty wherever possible
5. Connect two close faults or tooth preparations(less than 0.5mm apart)
6. Restrict the depth of the preparation into dentin to a maximum of 0.2-0.5mm.

18. ROTARY instrument axis perpendicular

19. Width of marginal ridge strength – MOLARS=2mm
PRE-MOLARS=1.6mm
Depth – 1.5mm , measured at central fissure
In CLASS II,III,IV
Proximally restrict the depth of axial wall pulpally to a maximum of
0.2-0.8mm into dentin
WIDTH OF THE CAVITY- 1/4th
of the intercuspal distance

20. PROXIMAL CLEARANCE- 0.2-0.3mm GINGIAL SEAT CLEARANCE- 0.5mm
CLEARANCE

21. REVERSE CURVE
When the direction of the mesiofacial wall is
parallel to the direction of the enamel rods,thus
creating a ‘S’ shaped curve in the proximal outline
It is created to:
• Provide butt joint in the
preparation margin
• To relieve the contact
• To place the proximal margins in
a self cleansing area

22. Reverse Curve
• In case of maxillary teeth, mostly the molars, the contact area is more buccally,
i.e.; the lingual embrasures are more than the buccal embrasures.
• In such cases, extending the bucco- proximal wall into the embrasure lead to
excessive cutting of the buccal cusps
• To avoid this, a reverse curve ( S- shaped) is made in the buccal proximal wall so
as to have sufficient amount of dentin in that area & also to achieve butt joint
with the cavosurface margins
• Such a curve, though mostly given in maxillary molars, can be given in any tooth
where the contact area is deviated or more pronounced on one side.

25. STEP 2: PRIMARY RESISTANCE FORM
• This is that shape and placement of the cavity walls that best enables
both the restoration and the tooth to withstand , without fracture ,
the masticatory forces delivered principally along the long axis of the
tooth.

26. PRINCIPLES
 Box shaped
 Flat floors
 Slight rounding of internal line angles
 Provide enough thickness of the restorative material
RESTORATIVE
MATERIAL
1. AMALGAM
2. CAST GOLD
3. PORCELAIN
4. COMPOSITE
MINIMAL
THICKNESS
REQUIRED
1.5mm
1-2mm
2.0mm
1-2mm

27. FEATURES:
1. Relatively flat floors
2. Box shape
3. Including all weakened tooth structure
4. Preservation of cusps and marginal ridges
5. Rounded internal line angles
6. Adequate thickness of the restorative material
7. Reduction of cusps for capping when indicated.

29. STEP:3 PRIMARY RETENTION FORM
It is that shape and form of the tooth preparation that resist displacement
or removal of the restoration from tipping or lifting forces. Often features
that enhance retention form also enhance resistance form.

30. PRINCIPLES
FOR AMALGAM
o Occlusal convergence
prevents lifting
o Occlusal dovetail prevents
tipping
FOR COMPOSITE
o Acid etching and bonding
provide micromechanical
retention
o Enamel bevels enhance
retention

31. ISTHMUS
It is the transition between the occlusal and proximal cavity . This is the narrowest place
of preparation and its fundamental significance for retention of the restoration

32. STEP:5 REMOVAL OF ANY REMAINING ENAMEL PIT OR FISSURE/
OLD RESTORATIVE MATERIAL
DEFINITION: This is the elimination of any infected carious tooth structure or
faulty restorative material that is left in the tooth after initial tooth preparation.
PRINCIPLES:
It exhibits two distinct areas;
1. Infected dentin
2. Affected dentin

33. INFECTED DENTIN
• More superficial layer
• Light brown in color
• Soft and leathery in consistency
• Not sensitive to touch
• Collagen is irreversibly denatured
• Has high concentration of bacteria
• Stained by caries detecting dyes
• Not remineralizable
• Should be removed
AFFECTED DENTIN
• Deeper layer
• Dark brown in color
• Hard in consistency
• Sensitive to touch
• Collagen is reversibly denatured
• No bacteria is found in this zone
• Not stained by caries detecting dyes
• Capable of remineralization
• Should be retained

35. HOW IS THE ELIMINATION DONE?
1. SPOON EXCAVATOR
2. ROUND STEEL BURS
3. ROUND CARBIDE BUR
4. SMALL BURS 2,4,6

36. INDICATION OF REMOVING OLD RESTORATIVE MATERIAL
• If esthetic is affected
• If it compromise the retention of new
restoration
• Evidence of secondary caries
• Pulp symptomatic
• There is marginal deterioration of
old restoration

37. STEP 6: PULP PROTECTION
• Deep dentin is very porous and susceptible to desiccation .
The thin remaining wall of dentin provides little protection from:
oHeat generated by rotary instruments during subsequent steps.
oNoxious ingredients of various restorative materials.
oThermal changes conducted through restorative material.
oForces transmitted through materials to dentin
oGalvanic shock
oThe ingress of bacteria or bacterial toxins through microleakage
Can be achieved by using cavity varnish, liners,base or bonding agents

38. STEP 6: PULP PROTECTION
Actually not a step
This step is achieved by using Cavity varnish
Liners
Bases
Bonding agents

39. REMAINING DENTIN THICKNESS
If RDT >2mm = No need of liner
If RDT 1-2mm= Cavity liner
If RDT <2mm= Cavity Base

40. STEP 7: SECONDARY RESISTANCE AND RETENTION FORM
This step is necessary in case of compound and complex cavity
preparation
2 types:
1. MECHANICAL
FEATURES
• Retention grooves and
coves
• Groove extention
• Skirts
• Beveled enamel
margins
• Pins , Slots , Steps and
Amalgapins
2.CONDITIONING
PROCEDURES

41. RETENTION GROOVES AND COVES
Provides extra retention for Class 2 preparation
Reduces proximal displacement of the restoration
1. RETENTION GROOVES- Class II Amalgam
Class II Cast metal restoration
2. RETENTION COVES- Class I , V Amalgam

43. GROOVE EXTENTION –
Additional retention of the restorative material may be obtained by
arbitratrily extending the preparation for molars onto facial and lingual
surface to include facial and lingual groove. Done for cast metal restoration
when indicated

44. SKIRTS-
Preparation features in cast-gold restoration that extend the
preparation around some ,if not all, of the line angles of the
tooth
It provides additional retention and resistance

45. BEVELED ENAMEL MARGINS-
This feature is provided for cast metal and composite restoration to produce better
marginal adaptation between the restoration and the tooth
In composite, bevels increases the surface area for etching thus improving bonding

46. PINS ,SLOTS, STEPS, AMALGAPINS
Used in amalgam restoration when need for increased retention
i.e, there is limited remaining tooth structure available to help retain the restoration
SLOTS:
Are given to increase surface area for the restoration
A 0.75-1.0mm deep and 1.0-3.0mm wide cut is given on the pulpal and/or cervical wall
This rectangular depression in these walls increases the bulk for the restoration and also
increases the area for holding

47. AMALGAPINS:
These pins are anchored in remaining sound dentin, protrude vertically above the
remaining tooth structure
Minimum : 0.8mm diameter
2mm deep

48. CONDITIONED PROCEDURES
INCLUDE : Etching and Bonding.
USED : GIC ,Composite, Ceramic restorations
Superficial demineralization of preparation walls and subsequent infiltration of
the altered surface with resin – based adhesives allows for increased retention and
resistance of restoration

49. STEP 8: FINISHING THE EXTERNAL WALLS OF
THE PREPARATION
DEFINITION: This is the further development , when indicated ,of a
specific cavosurface design and degree of smoothness that produces
the maximum effectiveness of the restorative material used
OBJECTIVES:
• Smooth marginal junction between restoration and tooth
• Provide close adaptation between restoration and tooth
• Marginal is maintained
• To provide maximum strength for both tooth and restoration

50. FEATURES:
• DESIGN OF THE CAVOSURFACE MARGIN:
For Amalgam - 90° cavosurface angle/butt joint
• DEGREE OF SMOOTHNESS OR ROUGHNESS OFTHE WALL
Rotary or Hand cutting instruments.
Plain cut fisure bur – smooth walls
Hatchets and GMT – plane enamel and smooth walls

52. STEP 9: FINAL PROCEDURE: CLEANING
INSPECTING , VARNISHING CONDITIONING
Debridement (cleaning) of the tooth preparation involves use of
air/water syringe to remive visible debris with water
In some instance ,debris clings to walls and angles despite the
forementioned efforts., and it may be necessary to loosen this materia
with an explorer or small cotton pellet.
It is important not to dehydrate the tooth by over use of air as it
may damage the odontoblasts associated with desiccated tubules
Varnish and Conditioning may be employed depending on the type
of restorative material

54. TUNNEL TOOTH PREPARATION
The tunnel tooth preparation joins the occlusal lesion with a proximal lesion by
means of prepared tunnel under the involved marginal ridge
For conservative preparation some investigators
advocate this
OBJECTIVE:
To remove the carious lesion and leave the marginal ridge essentially intact
DRABACK:
The development of appropriately formed preparation walls may be compromised by lack of access and visibility
Complete excavation of the carious lesion is not predictable
Preservation of the marginal ridge strength is questionable
AMALGAM
COMPOSITE
GIC

55. CONCLUSION
 Caivity design should be biologica and structural harmony with the
tissues of the teeth
 Outline,depth, width, retention,resistance etc should be decided
according to the nature of the disease,properties of the tooth tissue
and the restorative material to be used
 Other factors: Occlusion, Pulp status, Esthetic , Tooth anatomy should
be considered

56. THANK YOU
JYOTHIKA.A
IIIrd year